Image processing apparatus having a digital image processing section including enhancement of edges in an image

ABSTRACT

An image processing apparatus includes: an image pickup section for converting an object light into image signals of Bayer RGB array; a color information detecting section for obtaining color information of the object from the image signals obtained by the image pickup section; a first luminance data generating section for finding luminance data for use in edge enhancement processing based on G signals of the image signals obtained by the image pickup section; a second luminance data generating section for finding luminance data for use in edge enhancement processing based on all color signals of the image signals; a selector for providing an output by switching between outputs of the first and second luminance data generating section; and a selection signal generating section for generating selection signal for controlling the switching of the selector based on color information obtained at the color information detecting section. The image processing apparatus is thereby achieved as capable of edge enhancement processing at favorable S/N and with less occurrence of edge noise in high saturation regions and low saturation regions.

This application is a divisional application of prior application Ser.No. 09/695,420 filed Oct. 25, 2000 now U.S. Pat. No. 6,816,193.

This application claims benefit of Japanese Application No. Hei11-304875 filed in Japan on Oct. 27, 1999, the contents of which areincorporated by this reference.

BACKGROUND OF THE INVENTION

The present invention relates to image processing apparatus, and moreparticularly to an image processing apparatus having a digital imageprocessing section including enhancement of edges in image to bedisplayed.

When an image is processed for edge enhancement, a technique isgenerally used to extract edge components within the image so as to addthe extracted edge components to the original image. In such case, theedge components to be added are obtained by extracting high-frequencycomponents of luminance signals of the image. In image pickup devicesusing RGB primary-color filter, the techniques for generating luminancesignal to extract such high-frequency components include: (1) techniquefor generating luminance signal by using only G (green) signals out ofall the color signals of RGB within the image; and (2) technique forgenerating luminance signal by using all the color signals of RGB in theimage.

An example of construction of conventional image processing apparatuswill now be explained by way of FIG. 1 in which such two techniques areused to generate luminance signal to perform edge enhancementprocessing. Referring to FIG. 1, numeral 101 denotes an image pickupmeans; image signals of Bayer RGB array are obtained from the imagepickup means 101. The Bayer RGB array image signals are subjected towhite balancing at a white balancing section 102. Luminance data arethen generated from 2G or (R+2G+B) /2 at a luminance data generatingsection 103 where R, G, B represent the outputs of the color signals ofR (red), G (green), B (blue), respectively. The luminance data are thenpassed through a high-pass filter 104 to extract edge components and thedegree of edge enhancement is adjusted at an edge enhancement adjustingsection 105 to form edge signals.

On the other hand, image signals after the white balancing are separatedof colors by pixel as a unit into RGB signals at color separationcircuit 106 and then subjected to color correction and γ correction at acolor correction/γ correction circuit 107. The RGB signals are convertedinto Y, Cr, Cb signals at YC conversion section 108. The above describededge signals are then added to the luminance signal Y outputted from YCconversion section 108 at an adder circuit 109 to obtain edge-enhancedluminance signal Y.

The above two techniques have their respective merits and demerits. Inparticular, FIG. 2A shows a part of image consisting of pixels of BayerRGB array. In such image of Bayer RGB array, two times of image signalsS are used in the case of generating luminance signal Y from 4 pixels ofRGB (R+2G+B) as shown in FIG. 2B as compared to the case of generatingluminance signal Y as shown in FIG. 2C from two pixels of G. Theresulting noise N, on the other hand, is only 2^(1/2) times from thetheory of noise reducer. For this reason, supposing S/N at the time ofgenerating from two pixels of G as 1/1=1, that at the time of generatingfrom 4 pixels of RGB becomes 2/2^(1/2)=2^(1/2). The case of generatingfrom 4 pixels of RGB becomes 2^(1/2) times better. Since, however, thesignals of R, B, which contain not much genuine luminance information,are used as luminance signal when 4 pixels of RGB are used, excessivelyemphasized edges are generated and defects occur especially at theportion of boundary between two highly saturated colors.

As has been described, there are merits and demerits in both the case ofusing only G signal and the case of using all the color signals of RGBin generating luminance signal. These are summarized in Table 1.

TABLE 1 Luminance signal Edge noise of high Edge noise of low generationmethod S/N saturation portion saturation portion From only G Bad SmallLarge From RGB Good Large Small

Prior-art techniques according to some specific documents will now bedescribed. Japanese patent application laid open Hei-10-108208 forexample discloses a technique in which contour signals (edge components)are extracted from G signals to perform edge enhancement. Further,Japanese patent laid open application Hei-9-261513 discloses a contour(edge) enhancing method in which two types of contour extractingmethods, i.e., MIX (mix) mode and NAM (non-average mix) mode areswitched to each other according to the saturation of image. Here, MIXmode refers to generation of contour enhancement signal after additionof a plurality of signals corresponding to the three primary colors ofRGB, etc., in the light of image to be displayed; NAM mode refers togeneration of contour enhancement signal by adding one selecting thesignal emphasized most in the direction of black and one selecting thesignal emphasized most in the direction of white out of the respectivecontour enhancement signals of the above described plurality of signals.

Thus the problem is that there are respective merits and demerits asdescribed above of the technique for generating luminance signal byusing only G signals in the image to extract edge components and thetechnique for generating luminance signal by using all the color signalsof RGB in the image to extract edge components. Further, the contourenhancement technique as disclosed in the above Japanese patent laidopen application Hei-9-261513 has a problem that, if Bayer RGB array isused as the color filter array of image pickup device, the mereswitching between the two types of contour extracting methods accordingto saturation alone may, depending on the colors of image, fall short ofsuitable processing due to lack of information. Furthermore, there is aproblem of complicated construction in the NAM mode, since it isnecessary to perform addition by respectively selecting one emphasizedmost in the direction of black and one emphasized most in the directionwhite out of the contour enhancement signals.

SUMMARY OF THE INVENTION

To eliminate the above problems in the conventional methods of edgeenhancement processing of an image, it is an object of the presentinvention to provide an image processing apparatus having a digitalimage processing section including edge enhancement processing of simpleconstruction having only the respective merits of the prior-arttechniques.

In accordance with a first aspect of the invention, there is provided animage processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; color informationdetection means for obtaining color information of the object from theimage signals obtained by the image pickup means; a first luminance datageneration means for finding luminance data for use in edge enhancementprocessing from G signals out of the image signals obtained by the imagepickup means; a second luminance data generation means for findingluminance data for use in edge enhancement processing from all colorsignals of the image signals obtained by the image pickup means; andluminance data switch means for providing an output by switching betweenoutputs of the first and second luminance data generation means based onthe color information obtained at the color information detection means.

By such construction, an output is provided on the basis of colorinformation obtained at the color information detection means byswitching between output of the first luminance data generation meansfor finding luminance data from G signal and output of the secondluminance data generation means for finding luminance data from allcolor signals of the image signals. Hence edge enhancing components canbe extracted on the basis of an optimal luminance data corresponding tothe color information, an edge enhancement processing is possible with afavorable S/N and with less edge noise in high saturation regions andlow saturation regions. The above object is thereby achieved.

It is another object of the invention to provide an image processingapparatus in which switching of the techniques for generating luminancedata for use in edge enhancement processing is smooth and the edgeenhancement processing is performed without unnaturalness.

In accordance with a second aspect of the invention, there is providedan image processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; color informationdetection means for detecting color information of the object from theimage signals obtained by the image pickup means; a mixed luminance datageneration means for generating mixed luminance data by mixing luminancedata for use in edge enhancement processing generated from G signals outof the image signals obtained by the image pickup means and luminancedata for use in edge enhancement processing generated from all colorsignals of the image signals with continuously changing the mixing ratio(including 1:0 and 0:1); and means for setting the mixing ratio at themixed luminance data generation means based on the color informationobtained at the color information detection means.

By such construction, mixed luminance data is generated on the basis ofcolor information by mixing the luminance data generated from G signaland the luminance data generated from all color signals withcontinuously changing the mixing ratio. Hence an optimal luminance datacorresponding to the color information can be smoothly changed, makingit possible to perform edge enhancement processing withoutunnaturalness. The above object is thereby achieved.

It is yet another object of the invention to provide an image processingapparatus in which an image processed of edge enhancement at favorableS/N can be obtained even for an image having frequent edge portions.

In accordance with a third aspect of the invention, there is provided animage processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; edge informationdetection means for detecting edge information of the object from theimage signals obtained by the image pickup means; a first luminance datageneration means for finding luminance data for use in edge enhancementprocessing from G signals out of the image signals obtained by the imagepickup means; a second luminance data generation means for findingluminance data for use in edge enhancement processing from all colorsignals of the image signals obtained by the image pickup means; andluminance data switch means for providing an output by switching betweenoutputs of the first and second luminance data generation means based onthe edge information obtained at the edge information detection means.

By such construction, an output is provided by switching between theluminance data generated from G signal and the luminance data generatedfrom all color signals on the basis of edge information obtained at theedge information detection means. Hence it becomes possible to performedge enhancement processing on the basis of an optimal luminance datacorresponding to the edge information even in an image having frequentedge portions. The above object is thereby achieved.

It is a further object of the invention to provide an image pickupapparatus in which, even for an image having frequent edge portions, thetechniques for generating luminance data for use in edge enhancement aresmoothly switched so that edge enhancement processing withoutunnaturalness can be performed.

In accordance with a fourth aspect of the invention, there is providedan image processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; edge informationdetection means for detecting edge information of the object from theimage signals obtained by the image pickup means; a mixed luminance datageneration means for generating mixed luminance data by mixing luminancedata for use in edge enhancement processing generated from G signals outof the image signals obtained by the image pickup means and luminancedata for use in edge enhancement processing generated from all colorsignals of the image signals with continuously changing the mixing ratio(including 1:0 and 0:1); and means for setting the mixing ratio at themixed luminance data generation means based on the edge informationobtained at the edge information detection means.

By such construction, mixed luminance data is generated on the basis ofedge information by mixing the luminance data generated from G signaland the luminance data generated from all color signals withcontinuously changing the mixing ratio. Hence an optimal luminance datacorresponding to the edge information can be smoothly changed so thatedge enhancement processing without unnaturalness can be performed evenin an image having frequent edge portions. The above object is therebyachieved.

It is a further object of the invention to provide an image processingapparatus in which an image as processed of edge enhancement atfavorable S/N can be obtained corresponding to the characteristic of anobject.

In accordance with a fifth aspect of the invention, there is provided animage processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; color informationdetection means for detecting color information of the object from theimage signals obtained by the image pickup means; edge informationdetection means for detecting edge information of the object from theimage signals obtained by the image pickup means; image regiondetermination means for determining the state of beingfrequent/infrequent of edge portions (frequency of occurrence per unitarea of those regarded as edges, i.e., degree of denseness/sparseness ofedges) in the object from the image signals obtained by the image pickupmeans; a first luminance data generation means for finding luminancedata for use in edge enhancement processing from G signals out of theimage signals obtained by the image pickup means; a second luminancedata generation means for finding luminance data for use in edgeenhancement processing from all color signals of the image signalsobtained by the image pickup means; luminance data switch means forproviding an output by switching between outputs of the first and secondluminance data generation means; a first selection signal generatingsection for generating a selection signal for controlling the switchingat the luminance data switch means based on color information obtainedat the color information detection means; a second selection signalgenerating section for generating a selection signal for controlling theswitching at the luminance data switch means based on edge informationobtained at the edge information detection means; and a selection signalswitching section for providing an output by switching between theselection signals of the first selection signal generating section andthe second selection signal generating section based on a determinationsignal from the image region determination means.

By such construction, an output is provided by switching between theselection signal for controlling the switching of the luminance dataswitch means based on color information and the selection signal forcontrolling the switching of the luminance data switch means based onedge information on the basis of the determination signal from the imageregion determination means for determining the state of beingfrequent/infrequent of the edge portions in an object. Hence the edgeenhancement processing at favorable S/N can be performed correspondingto the characteristic of the object. The above object is therebyachieved.

It is a further object of the invention to provide an image processingapparatus in which, corresponding to the characteristic of an object, animage is obtained as processed of edge enhancement processing withoutunnaturalness where S/N is favorable and the techniques for generatingluminance data for use in the edge enhancement processing are switchedsmoothly.

In accordance with a sixth aspect of the invention, there is provided animage processing apparatus having a processing section for enhancingedges in an image, including: image pickup means for converting anobject light into image signals of Bayer RGB array; color informationdetection means for detecting color information of the object from theimage signals obtained by the image pickup means; edge informationdetection means for detecting edge information of the object from theimage signals obtained by the image pickup means; image regiondetermination means for determining the state of beingfrequent/infrequent of edge portions in the object from the imagesignals obtained by the image pickup means; a mixed luminance datageneration means for generating mixed luminance data by mixing luminancedata for use in edge enhancement processing generated from G signals outof the image signals obtained by the image pickup means and luminancedata for use in edge enhancement processing generated from all colorsignals of the image signals with continuously changing the mixing ratio(including 1:0 and 0:1); a first mixing ratio setting means for settingthe mixing ratio at the mixed luminance data generation means based onthe color information obtained at the color information detection means;a second mixing ratio setting means for setting the mixing ratio at themixed luminance data generation means based on the edge informationobtained at the edge information detection means; and a mixing ratiosetting signal switching section for providing an output by switchingbetween setting signals of the first mixing ratio setting means and thesecond mixing ratio setting means based on a determination signal fromthe image region determination means.

By such construction, an output is provided, on the basis of thedetermination signal from the image region determination means fordetermining the state of being frequent/infrequent of edge portions ofthe object, by switching between the setting signal of the first mixingratio setting means for setting the mixing ratio at the mixed luminancedata generation means based on the color information and the settingsignal of the second mixing ratio setting means for setting the mixingratio at the mixed luminance data generation means based on the edgeinformation. Hence edge enhancement processing without unnaturalness canbe performed at favorable S/N and smoothly corresponding thecharacteristic of the object. The above object is thereby achieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing can be performed without causing unnaturalness at the jointportions.

In accordance with a seventh aspect of the invention, there is providedan image processing apparatus having a joining processing section forjoining a plurality of images to generate one piece of image and aprocessing section for enhancing edges in an image, including: imagepickup means for converting an object light into image signals of BayerRGB array; color information detection means for obtaining colorinformation of the object from the image signals obtained by the imagepickup means; joint determination means for detecting joint informationof the image signals obtained by the image pickup means; a firstluminance data generation means for finding luminance data for use inedge enhancement processing from G signals out of the image signalsobtained by the image pickup means; a second luminance data generationmeans for finding luminance data for use in edge enhancement processingfrom all color signals of the image signals obtained by the image pickupmeans; and luminance data switch means for providing an output byswitching between outputs of the first and second luminance datageneration means based on the color information obtained at the colorinformation detection means and the joint information obtained from thejoint determination means.

By such construction, on the basis of the color information and jointinformation, an output is provided by switching between the output ofthe first luminance data generation means for finding luminance datafrom G signals and the output of the second luminance data generationmeans for finding luminance data from all color signals. Hence, injoining a plurality of images, edge enhancement processing can beperformed without unnaturalness at the joint portions. The above objectis thereby achieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing can be performed smoothly and without unnaturalness at thejoint portions.

In accordance with an eighth aspect of the invention, there is providedan image processing apparatus having a joining processing section forjoining a plurality of images to generate one piece of image and aprocessing section for enhancing edges in an image, including: imagepickup means for converting an object light into image signals of BayerRGB array; color information detection means for obtaining colorinformation of the object from the image signals obtained by the imagepickup means; joint determination means for detecting joint informationof the image signals obtained by the image pickup means; a mixedluminance data generation means for generating mixed luminance data bymixing luminance data for use in edge enhancement processing generatedfrom G signals out of the image signals obtained by the image pickupmeans and luminance data for use in edge enhancement processinggenerated from all color signals of the image signals with continuouslychanging the mixing ratio (including 1:0 and 0:1); and means for settingthe mixing ratio at the mixed luminance data generation means based onthe color information obtained at the color information detection meansand the joint information obtained from the joint determination means.

By such construction, on the basis of the color information and jointinformation, mixed luminance data is generated by mixing the luminancedata generated from G signal and the luminance data generated from allcolor signals with continuously changing the mixing ratio. Hence, injoining a plurality of images, edge enhancement processing can beperformed smoothly and without unnaturalness at the joint portions. Theabove object is thereby achieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing without causing unnaturalness at the joint portions can beperformed even for an image having frequent edge portions.

In accordance with a ninth aspect of the invention, there is provided animage processing apparatus having a joining processing section forjoining a plurality of images to generate one piece of image and aprocessing section for enhancing edges in an image, including: imagepickup means for converting an object light into image signals of BayerRGB array; edge information detection means for obtaining edgeinformation of the object from the image signals obtained by the imagepickup means; joint determination means for detecting joint informationof the image signals obtained by the image pickup means; a firstluminance data generation means for finding luminance data for use inedge enhancement processing from G signals out of the image signalsobtained by the image pickup means; a second luminance data generationmeans for finding luminance data for use in edge enhancement processingfrom all color signals of the image signals obtained by the image pickupmeans; and luminance data switch means for providing an output byswitching between outputs of the first and second luminance datageneration means based on the edge information obtained at the edgeinformation detection means and the joint information obtained from thejoint determination means.

By such construction, on the basis of the edge information and jointinformation, an output is provided by switching between the output ofthe first luminance data generation means for finding luminance datafrom G signals and the output of the second luminance data generationmeans for finding luminance data from all color signals. Hence, injoining a plurality of images, edge enhancement processing withoutunnaturalness at the joint portions can be performed even for an imagehaving frequent edge portions. The above object is thereby achieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing can be performed smoothly and without causing unnaturalnessat the joint portions even for an image having frequent edge portions.

In accordance with a tenth aspect of the invention, there is provided animage processing apparatus having a joining processing section forjoining a plurality of images to generate one piece of image and aprocessing section for enhancing edges in an image, including: imagepickup means for converting an object light into image signals of BayerRGB array; edge information detection means for obtaining edgeinformation of the object from the image signals obtained by the imagepickup means; joint determination means for detecting joint informationof the image signals obtained by the image pickup means; a mixedluminance data generation means for generating mixed luminance data bymixing luminance data for use in edge enhancement processing generatedfrom G signals out of the image signals obtained by the image pickupmeans and luminance data for use in edge enhancement processinggenerated from all color signals of the image signals with continuouslychanging the mixing ratio (including 1:0 and 0:1); and means for settingthe mixing ratio at the mixed luminance data generation means based onthe edge information obtained at the edge information detection meansand the joint information obtained from the joint determination means.

By such construction, on the basis of the edge information and jointinformation, mixed luminance data is generated by mixing the luminancedata generated from G signal and the luminance data generated from allcolor signals with continuously changing the mixing ratio. Hence, injoining a plurality of images, edge enhancement processing can beperformed smoothly and without unnaturalness at the joint portions evenfor an image having frequent edge portions. The above object is therebyachieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing can be performed corresponding to the characteristic of anobject at favorable S/N and without unnaturalness at the joint portions.

In accordance with an eleventh aspect of the invention, there isprovided an image processing apparatus having a joining processingsection for joining a plurality of images to generate one piece of imageand a processing section for enhancing edges in an image, including:image pickup means for converting an object light into image signals ofBayer RGB array; color information detection means for obtaining colorinformation of the object from the image signals obtained by the imagepickup means; edge information detection means for detecting edgeinformation of the object from the image signals obtained by the imagepickup means; image region determination means for determining the stateof being frequent/infrequent of edge portions in the object from theimage signals obtained by the image pickup means; joint determinationmeans for detecting joint information of the image signals obtained bythe image pickup means; a first luminance data generation means forfinding luminance data for use in edge enhancement processing from Gsignals out of the image signals obtained by the image pickup means; asecond luminance data generation means for finding luminance data foruse in edge enhancement processing from all color signals of the imagesignals obtained by the image pickup means; luminance data switch meansfor providing an output by switching between outputs of the first andsecond luminance data generation means; a first selection signalgenerating section for generating a selection signal for controlling theswitching at the luminance data switch means based on color informationobtained at the color information detection means; a second selectionsignal generating section for generating a selection signal forcontrolling the switching at the luminance data switch means based onedge information obtained at the edge information detection means; and aselection signal switching section for providing an output by switchingbetween the selection signals of the first selection signal generatingsection and of the second selection signal generating section based onthe joint information of image from the joint determination means forjoint boundary portions of image and based on a determination signalfrom the image region determination means for those other than the jointboundary portions of image.

By such construction, an output is provided by switching between theselection signal for controlling the switching of the luminance dataswitch means based on color information and the selection signal forcontrolling the switching of the luminance data switch means based onedge information on the basis of the joint information of image forjoint boundary portions of image and on the basis of the determinationsignal of the image region determination means for those other than thejoint boundary portions of image. Hence, in performing joiningprocessing, the edge enhancement processing can be performedcorresponding to the characteristic of the object at favorable S/N andwithout unnaturalness at the joint portions. The above object is therebyachieved.

It is a further object of the invention to provide an image processingapparatus in which, when joining a plurality of images, edge enhancementprocessing can be performed corresponding to the characteristic of anobject smoothly at favorable S/N and without unnaturalness at the jointportions.

In accordance with a twelfth aspect of the invention, there is providedan image processing apparatus having a joining processing section forjoining a plurality of images to generate one piece of image and aprocessing section for enhancing edges in an image, including: imagepickup means for converting an object light into image signals of BayerRGB array; color information detection means for obtaining colorinformation of the object from the image signals obtained by the imagepickup means; edge information detection means for detecting edgeinformation of the object from the image signals obtained by the imagepickup means; image region determination means for determining the stateof being frequent/infrequent of edge portions in the object from theimage signals obtained by the image pickup means; joint determinationmeans for detecting joint information of the image signals obtained bythe image pickup means; a mixed luminance data generation means forgenerating mixed luminance data by mixing luminance data for use in edgeenhancement processing generated from G signals out of the image signalsobtained by the image pickup means and luminance data for use in edgeenhancement processing generated from all color signals of the imagesignals with continuously changing the mixing ratio (including 1:0 and0:1); a first mixing ratio setting means for setting the mixing ratio atthe mixed luminance data generation means based on the color informationobtained at the color information detection means; a second mixing ratiosetting means for setting the mixing ratio at the mixed luminance datageneration means based on the edge information obtained at the edgeinformation detection means; and a mixing ratio setting signal switchingsection for providing an output by switching between setting signals ofthe first mixing ratio setting means and of the second mixing ratiosetting means based on the joint information of image signals from thejoint determination means for joint boundary portions of image and basedon a determination signal from the image region determination means forthose other than the joint boundary portions of image.

By such construction, an output is provided as switched between thesetting signal of the first mixing ratio setting means for setting themixing ratio of the mixed luminance data generation means based on colorinformation and the setting signal of the second mixing ratio settingmeans for setting the mixing ratio of the mixed luminance datageneration means based on edge information on the basis of the jointinformation of image for joint boundary portions of image and on thebasis of the determination signal of the image region determinationmeans for those other than the joint boundary portions of image. Hence,in joining a plurality of images, the edge enhancement processing can beperformed corresponding to the characteristic of the object smoothly atfavorable S/N and without unnaturalness at the joint portions. The aboveobject is thereby achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of construction ofconventional image processing apparatus for performing the edgeenhancement processing.

FIGS. 2A, 2B and 2C show a portion of Bayer RGB array image, the mannerfor generating luminance signal from four pixels of RGB and the mannerfor generating luminance signal from two pixels of G, respectively.

FIG. 3 is a block diagram showing a first embodiment of the imageprocessing apparatus according to the present invention.

FIG. 4 shows saturation in a chromaticity diagram where Cr, Cb colorsignals of a primary-color filter image are the axes of coordinates.

FIG. 5 shows hue in a chromaticity diagram where Cr, Cb color signals ofa primary-color filter image are the axes of coordinates.

FIG. 6 shows “saturation+hue” in a chromaticity diagram where Cr, Cbcolor signals of a primary-color filter image are the axes ofcoordinates.

FIG. 7 is a block diagram showing a second embodiment of the invention.

FIG. 8 shows a technique for setting a weighting factor based onsaturation.

FIG. 9 shows another technique for setting a weighting factor based onsaturation.

FIG. 10 shows yet another technique for setting a weighting factor basedon saturation.

FIG. 11 shows a technique for setting a weighting factor based on hue.

FIG. 12 shows another technique for setting a weighting factor based onhue.

FIG. 13 is a block diagram showing a third embodiment of the invention.

FIG. 14 is a block diagram showing a fourth embodiment of the invention.

FIG. 15 shows a technique for setting a weighting factor based on edgeinformation.

FIG. 16 shows another technique for setting a weighting factor based onedge information.

FIG. 17 shows yet another technique for setting a weighting factor basedon edge information.

FIG. 18 is a block diagram showing a fifth embodiment of the invention.

FIG. 19 is a block diagram showing a sixth embodiment of the invention.

FIG. 20 is a block diagram showing a seventh embodiment of theinvention.

FIG. 21 is a block diagram showing an eighth embodiment of theinvention.

FIG. 22 is a block diagram showing a ninth embodiment of the invention.

FIG. 23 is a block diagram showing a tenth embodiment of the invention.

FIG. 24 is a block diagram showing an eleventh embodiment of theinvention.

FIG. 25 is a block diagram showing a twelfth embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some embodiments will now be described. FIG. 3 is a block diagramshowing a first embodiment of the image processing apparatus accordingto the present invention. Included in FIG. 3 are: image pickup means 1for outputting image signals of Bayer RGB array; a white balancingsection 2; a color separation circuit 3 for separating the image signalsinto RGB signals by pixel as a unit; a color-correction/γ-correctioncircuit 4; YC conversion circuit 5; color information detection means 6for detecting color information based on Cr, Cb color signals outputtedfrom YC conversion circuit 5; a selection signal generating section 7for generating a selection signal based on color information signaloutputted from the color information detection means 6: a firstluminance data generating section 8 for generating luminance data foruse in edge enhancement based on G signals of the image signalsprocessed of white balancing at the white balancing section 2; a secondluminance data generating section 9 for generating luminance data foruse in edge enhancement based on (R+2G+B)/2 of the image signals; aselector 10 for selectively outputting one or the other of the luminancedata from the first luminance data generating section 8 and theluminance data from the second luminance data generating section 9 onthe basis of the selection signal from the selection signal generatingsection 7; a high-pass filter 11 for extracting edge components from theselectively outputted luminance data; an edge enhancement magnitudeadjusting section 12; and an adder circuit 13 for adding edge signalsadjusted of enhancement magnitude to luminance signals Y from the YCconversion circuit 5.

A description will now be given with respect to operation of the firstembodiment constructed as the above. It is the same as in a conventionalexample up to the point that Bayer RGB array signals obtained from imagepickup means 1, after processed at white balancing section 2, areseparated of colors into RGB signals at the color separation circuit 3,processed of color correction and γ correction at thecolor-correction/γ-correction circuit 4 and subjected to YC conversionat YC conversion circuit 5. In the first embodiment according to theinvention, color information is detected at the color informationdetection means 6 on the basis of Cr, Cb color signals obtained from YCconversion circuit 5 and, based on such color information, a selectionsignal is generated at the selection signal generating section 7.

Further, Bayer RGB array image signals from the image pickup means 1after processed of white balancing are inputted to each of the first andsecond luminance data generating sections 8 and 9. Luminance data basedon 2G signal is generated from the first luminance data generatingsection 8 and luminance data based on (R+2G+B)/2 signal is generatedfrom the second luminance data generating section 9, both being inputtedto selector 10. Based on the selection signal from the selection signalgenerating section 7, one or the other of the luminance datacorresponding to color information is then selectively outputted fromthe selector 10. The edge components of the selected luminance data areextracted through the high-pass filter 11 and edge signals adjusted ofedge enhancement magnitude are generated at the edge enhancementmagnitude adjusting section 12. The edge signals are then added to theluminance signals Y from YC conversion circuit 5 at the adder circuit 13to perform edge enhancement processing.

A suitable luminance data for use in edge enhancement processing isthereby selected corresponding to the color information to generate edgesignals. In connection with saturation, in particular, edge signals inthe case of low saturation are generated by using the luminance datafrom the second luminance data generating section 9 and edge signals inthe case of high saturation are generated by using the luminance datafrom the first luminance data generating section 8. An edge enhancementprocessing is thus performed at favorable S/N and with less edge noisein a low-saturation image or in a high-saturation image. Further, inconnection with hue, edge signals are generated by using the luminancedata from the second luminance data generating section in the case ofspecific hues such as G, magenta (Mg) and by using the first luminancedata in the case of other hues. An edge enhancement processing isthereby performed corresponding to hues of the image object at favorableS/N and with less edge noise.

A detailed description will now be given with respect to detection ofcolor information to be performed at the color information detectionmeans 6. First, there are three types of color information to bedetected from Cr, Cb signals, i.e., saturation, hue, and saturation andhue of image. Further, the techniques for detecting color informationand for switching of luminance data based on the same include: atechnique for detecting color information of each pixel of an objectimage; a technique for detecting an average color information for awhole object image; a technique for detecting an average colorinformation of a whole frame from the color information of specificsampling portions of an object image; and techniques for switchingluminance data based on these.

The fundamental technique for detection and switching of colorinformation is to detect and switch color information for every pixel.According to this technique, a suitable edge enhancement processing atfavorable S/N is possible even when pixels of chromatic color andachromatic color are mixed within an object image. On the other hand,the technique for switching by detecting an average color informationfor a whole object has an advantage that an edge enhancement withoutunnaturalness can be achieved because of the elimination of switchingpoints, though there is a possibility that an accurate processing cannotbe performed for some portions when pixels of chromatic colors andachromatic colors are mixed. Further, the technique for switching bydetecting color information from specific sampling data is amodification of the above technique for switching by detecting anaverage color information of the whole object. It is a technique forswitching by detecting an average color information of a whole frame byusing data of pixels sampled at specific intervals instead of data ofthe whole frame and has an advantage that the size can be reduced of theoperation unit and memory in the color information detection means.

A description will now be given with respect to actual methods ofdetection in the respective cases where saturation or hue or“saturation+hue” is used as the color information. First, the techniquefor detecting saturation from Cr, Cb color signals will be described byway of FIG. 4. FIG. 4 is a chromaticity diagram where Cr, Cb colorsignals are the axes of coordinates in a primary-color filter image sothat saturation C1 in the case of Cr, Cb signals being Cr1, Cb1,respectively, is represented by distance from the origin on thechromaticity diagram. In particular, C1 is expressed as:C1=(Cb1² +Cr1²)^(1/2)  (1)

If the detected saturation C1 is a high saturation, then, a selectionsignal is generated from the selection signal generating section 7 sothat the luminance data from the first luminance data generating section8 is selected at selector 10. If saturation C1 is a low saturation, onthe other hand, a selection signal is generated from the selectionsignal generating section 7 so that the luminance data from the secondluminance data generating section 9 is selected at selector 10.

The technique for detecting hue as color information from Cr, Cb signalswill now be described by way of a chromaticity diagram of FIG. 5. Asshown in FIG. 5, hue θc is represented by an angle for example from theCb axis on the chromaticity diagram. (It is supposed that phase isrepresented on the basis of the first quadrant of the chromaticitydiagram.) In particular, hue θc is expressed as:θc=tan⁻¹(Cr1/Cb1)  (2)

If the detected hue θc is G or Mg, then, a selection signal is generatedso that selector 10 selects the luminance data from the second luminancedata generating section 9 which generates luminance data for use in theextraction of edge components based on (R+2G+B)/2 of image signals. Ifhue θc is one of those other than G or Mg, on the other hand, aselection signal is generated so that the selector 10 selects theluminance data from the first luminance data generating section 8 whichgenerates luminance data for use in the extraction of edge componentsbased on 2G of image signals.

The technique for detecting “saturation+hue” as the color informationfrom Cr, Cb color signals will now be described by way of a chromaticitydiagram of FIG. 6. As shown in FIG. 6, “saturation+hue” C2 is found asdistance from saturation C to a straight line L which connects G and Mgon the chromaticity diagram. A value is thereby obtained as alsoconsidering hue. This will be further described below. Supposing G-Mgline L as y=ax (passing through the origin), distance C2 between G-Mgline and point C (Cb2, Cr2) is found as follows. First, since aperpendicular VL to line L from C is a straight line having aninclination of −1/a and passing through point (Cb2, Cr2), it isexpressed as y=−x/a+Cr2+Cb2/a. Next, an intersection (Cb3, Cr3) betweenline L and perpendicular VL is obtained as Cb3=(a×Cr2+Cb2)/(a²+1),Cr3=a×Cb3 by solving simultaneous equations of L and VL. Hence distance(saturation+hue) C2 between point (Cb2, Cr2) and point (Cb3, Cr3) isexpressed by the following expression (3), i.e., can be found from thevalues of Cb2, Cr2, and a.C2={(Cb2−Cb3)²+(Cr2−Cr3)²}^(1/2)  (3)

In this manner, if “saturation+hue” is used as the color information, amode is achieved as considering both hue and saturation. Luminance databased on 2G is selected only in the case where it is determined toselect luminance data based on 2G in each of using the color informationof saturation and using that of hue. Luminance data based on (R+2G+B)/2is selected in any other cases.

Table 2 summarizes luminance data to be selected for use in edgeenhancement processing in the cases as described above respectivelyusing saturation, hue, and “saturation+hue” as the color information tobe detected.

TABLE 2 Saturation + Subject color Saturation only Hue only hue Low G,Mg RGB RGB RGB Saturation Other colors RGB 2G RGB High G, Mg 2G RGB RGBSaturation Other colors 2G 2G 2G

A second embodiment of the invention will now be described. FIG. 7 is ablock diagram showing the second embodiment where like components as inthe first embodiment shown in FIG. 3 are denoted by like numerals anddescription thereof will be omitted. In this embodiment, provided as theluminance data generating section is a single mixed luminance datagenerating section 21 where luminance data based on 2G and luminancedata based on (R+2G+B)/2 can be generated and at the same time it iscaused to generate mixed luminance data thereof with continuouslychanging the mixing ratio between the two. Further, a weighting factorgenerating section 22 is provided as a means for setting a mixing ratioin order to control the mixing ratio at the mixed luminance datagenerating section 21. The weighting factor generating section 22generates weighting factor a on the basis of color information detectedby the color information detection means 6. It should be noted that thisembodiment is applied only to the case where luminance data is switchedfor every pixel.

At the above mixed luminance data generating section 21, luminance dataY is generated in the manner of:Y=2G×a+(R+B)×(1−a)  (4)where a is the weighting factor generated at the weighting factorgenerating section 22. If factor a is 1, luminance data based on 2G isgenerated. If factor a is 0.5, luminance data based on (R+2G+B)/2 isgenerated. For the cases of factor a being between 0.5 and 1, luminancedata is generated as a mixture of the two. It is thereby possible toeliminate unnaturalness in edge enhancement at boundary portions whereluminance data is switched.

A description will now be given with respect to methods for settingweighting factor a in the intermediate transient region when theweighting factor to be generated is set on the basis of colorinformation. First, setting of weighting factor a based on saturationinformation will be described by way of FIG. 8. In the technique forsetting weighting factor a in the setting example shown in FIG. 8,factor a is set to 0.5 when saturation C is a saturation lower than s(low saturation threshold). Thereby Y=2G×a+(R+B)(1−a)=(R+2G+B)/2 isobtained at the mixed luminance data generating section 21 whereluminance data based on this is generated. Factor a is set to 1 whensaturation C is a high saturation higher than t (high saturationthreshold). Y=2G×a+(R+B)(1−a)=2G is thereby obtained and luminance databased on this is generated.

When saturation C is s<C<t, i.e., if saturation of image is within amedium range, factor a becomes a=m(C−s)+0.5. Here m is an inclinationand is expressed as m 0.5/(t−s). In this manner, weighting factor a isrectilinearly changed in the intermediate transient region and, based onthis, the mixed luminance data is generated. In this setting example,since the weighting factor in the intermediate transient region isrectilinearly changed, operation is simple in generating the weightingfactor and luminance data in the transient region.

Another example of setting of weighting factor based on saturationinformation will now be described by way of FIG. 9. The settingtechnique of weighting factor a in this setting example is identical tothe foregoing setting example in that: when saturation C is a lowsaturation lower than s, factor a is set to 0.5 and luminance data isthereby generated based on Y=2G×a+(R+B)(1−a)=(R +2G+B)/2 at the mixedluminance data generating section 21; and, when saturation C is a highsaturation higher than t, factor a is set to 1 and luminance data basedon Y=2G×a+(R+B)(1−a)=2G is thereby generated at the mixed luminance datagenerating section 21. When saturation C is s<C<t in this settingexample, i.e., if saturation of image is in the medium transient region,factor a is set as having a functional relationship {a=F(C)} so that itis changed smoothly as curved from 0.5 to 1.

In this case, luminance data based on Y=2G×F(C)+(R+B) {1−F(C)} isgenerated from the mixed luminance data generating section 21.Accordingly, since weighting factor a is smoothly changed in theintermediate saturation region between the low saturation region and thehigh saturation region, a smooth change is possible of the luminancedata at the boundary of each region and of edge signals based on thesame for use in enhancement processing.

Yet another example of setting of weighting factor based on saturationinformation will now be described by way of FIG. 10. In this settingexample, the weighting factor a for the lowest saturation portion ofimage signals is set to 0.5 and the weighting factor a for the highestsaturation portion is set to 1. Weighting factor a between these is setas having a functional relationship {a=F(C) } indicating a curvesmoothly connecting the low saturation region, medium saturation regionand high saturation region between these irrespective of the thresholdvalues s, t.

In this case, luminance data is generated on the basis ofY=2G×F(C)+(R+B) {1−F(C)} from the mixed luminance data generatingsection 21. Accordingly, weighting factor a can be changed smoothly inthe manner of a curve over the regions of saturation and the luminancedata based on the same and edge signals for use in enhancementprocessing can be outputted as even more smoothly changed.

The setting of an intermediate transient region of weighting factor a inthe case of using hue as color information will now be described by wayof FIG. 11. In the setting technique of weighting factor a in thesetting example shown in FIG. 11, the weighting factor a is set to 0.5when hue θ is of the value indicating G or Mg. Luminance data based onY=(R+2G+B)/2 is thereby generated at the mixed luminance data generatingsection 21. If by contrast the weighting factor a is set to 1 when hue θis of a value indicating one other than G and Mg, a steep change resultsand there is a fear that noise or the like occurs at the boundaryportions. Hence the weighting factor a is set to 1 when hue θ is of avalue other than those in the vicinity of G and Mg; and luminance databased on Y=2G is thereby generated. On the other hand, when hue θ is ofa value indicating the vicinity of C or Mg, the weighting factor a isset so that it is changed along a straight line connecting 0.5 and 1.Luminance data is thereby generated based on what is obtained by causingthe mixing ratio of (R+2G+B)/2 and 2G be changed when hue θ is in thevicinities of G and Mg and hence a steep change is avoided. In thiscase, since the weighting factor a in the transient region in thevicinities of G and Mg is caused to change along a straight line,arithmetic of weighting factor a or the like in the transient region canbe readily performed.

Another example of setting of weighting factor based on hue informationwill now be described by way of FIG. 12. The setting of weighting factora in this setting example is identical to the foregoing setting examplein that: when hue θ is of a value indicating G or Mg, the weightingfactor a is set to 0.5 and luminance data based on Y=(R+2G+B)/2 isthereby generated at the mixed luminance data generating section 21;and, when hue θ is of a value indicating one outside the vicinity of Gor Mg, factor a is set to 1 and luminance data based on Y=2G is therebygenerated at the mixed luminance data generating section 21. In thissetting example, when hue θ is in the vicinity of G or Mg, factor a isset as having a relationship changed smoothly in a curve from 0.5 to 1.

In this case, luminance data is generated from the mixed luminance datagenerating section 21 on the basis of what is obtained by smoothlychanging the mixing ratio of Y=(R+2G+B)/2 and Y=2G. Accordingly, sincethe weighting factor a with hue θ being in the vicinities of G and Mg issmoothly changed, a smooth change is possible of the luminance data atsuch boundary regions and edge signals based on the same for use inenhancement processing.

The method shown in the above setting example is to set weighting factora to 1 when hue θ is of a value indicating the outside the vicinity of Gor Mg. However, it is also possible to set so that, when hue θ is of avalue indicating one other than G or Mg, the weighting factor a iscaused to be changed in a curve so that it has an arbitrary valuebetween 0.5 and 1 for those hues other than G or Mg. While settingweighting factor as having arbitrary values for the hues other than G orMg, a smooth change is thereby possible of luminance data as well asedge signals for use in enhancement processing as based on the hueregion of G or Mg and other hue regions.

A third embodiment will now be described. FIG. 13 is a block diagramshowing the third embodiment wherein the like components as in the firstand second embodiments shown in FIG. 3 and FIG. 7 are denoted by likereference numerals and description thereof will be omitted. Thisembodiment is constructed such that a means for generating luminancedata for use in edge enhancement is switched by using edge informationof image instead of color information of image. In particular, an edgedetection means 31 is provided to primarily detect a rough informationof edges in an image, i.e., whether it is an edge portion or not, fromBayer RGB array image signals after subjected to white balancing. Aselection signal is generated from a selection signal generating section32 on the basis of such edge information from the edge detection means31. Based on this selection signal, luminance data is selected from oneor the other of the first luminance data generating section 8 and thesecond luminance data generating section 9. In other words, luminancedata based on Y=2G from the first luminance data generating section 8 isselected when edges exist; and luminance data based on Y=(R+2G+B)/2 fromthe second luminance data generating section 9 is selected when edgesare not detected. Edge components are then extracted in a similar manneras in the first and second embodiments from the selected luminance datato generate edge signals for use in the enhancement processing by meansof addition.

By thus using image edge information for the switching of luminance datageneration, the generation method of luminance data is suitably switchedcorresponding to the object so that an image enhanced of edges atfavorable S/N can be obtained corresponding to the object. Whenluminance data of the first luminance data generating section 8 isselected to use luminance data generated based only on one color of G,the luminance data can then be obtained as having favorable S/N in ahigh saturation image. On the other hand, when luminance data of thesecond luminance data generating section 9 is selected to use theluminance data generated based on all of the colors, luminance data canbe obtained as having favorable S/N in a low saturation image.

Further, in finding edges from an image at the above edge detectionmeans 31, either Y=(R+2G+B)/2 or Y=2G can be used as luminance signal.If Y=(R+2G+B)/2 is used as the luminance signal, all color edges can bedetected. If Y=2G is used as the luminance signal, arithmetic at theedge detection means is easier. It should be noted that, at the aboveedge detection means 31, spatial frequency of the luminance signal basedon (R+2G+B)/2 or 2G is detected and edge information is found from thevalue thereof. The spatial frequency is detected for example byinvestigating luminance amplitude in vertical and horizontal directionswithin a very small area.

Further, in switching the luminance data generating technique on thebasis of edge information detected at the above edge detection means,the luminance data generating technique for a whole frame can beswitched based on the detected edge information, or the luminance datagenerating technique for every pixel can be switched based on thedetected edge information. If the luminance data generating techniquefor the whole frame is switched, luminance data without unnaturalnesscan be generated due to the fact that there is no switching point foreach pixel. On the other hand, if the generating technique of luminancedata is switched for every pixel within the object, luminance datahaving favorable S/N can be obtained even in an object where lowsaturation and high saturation are mixed.

A fourth embodiment will now be described. FIG. 14 is a block diagramshowing the fourth embodiment wherein the like components as in thefirst to third embodiments shown in FIGS. 3, 7 and 13 are denoted bylike reference numerals and description thereof will be omitted. Thisembodiment is achieved by applying certain portions of the secondembodiment to the third embodiment. Provided as the luminance datagenerating section is a single mixed luminance data generating section21 in which luminance data based 2G and luminance data based on(R+2G+B)/2 can be generated and at the same time it is possible togenerate mixed luminance data thereof with continuously changing themixing ratio between the two. Further, a weighting factor generatingsection 33 is provided for controlling the mixed luminance datagenerating section 21. The weighting factor generating section 33generates weighting factor a on the basis of edge information detectedby the edge information detection means 31. It should be noted that thisembodiment is applied only to the case where the manner of generatingluminance data is switched for every pixel.

At the above mixed luminance data generating section 21, luminance dataY is generated in the mode as indicated by the above expression (4). Ifweighting factor a is 1, luminance data based on 2G is generated. Ifweighting factor a is 0.5, luminance data based on (R+2G+B)/2 isgenerated. For the cases of weighting factor a being between 0.5 and 1,luminance data is generated with continuously changing the mixing ratiobetween the two. It is thereby possible to eliminate unnaturalness atboundaries where luminance data is switched.

A description will now be given with respect to methods for settingweighting factor a for the intermediate transient region when theweighting factor a to be generated is set on the basis of edgeinformation. First, a first setting method of weighting factor a basedon edge information will be described by way of FIG. 15. In setting ofweighting factor a in the setting example shown in FIG. 15, weightingfactor a is set to 0.5 when spatial frequency f detected at the edgedetection means 31 is in a low-frequency region (where edges do notexist) lower than a low-frequency threshold s. Luminance data based on(R+2G+B)/2 is thereby generated at the mixed luminance data generatingsection 21. The weighting factor a is set to 1 when the detected spatialfrequency f is in a high-frequency region (where edges exist) higherthan a high-frequency threshold t. Luminance data based on 2G is therebygenerated at the mixed luminance data generating section 21.

On the other hand, if the detected spatial frequency f is s<f<t, theweighting factor a becomes a=m(f−s)+0.5. Here, m is an inclination andexpressed as m=0.5/(t−s). In this manner, the weighting factor a isrectilinearly changed in the medium transient region and, based on this,mixed luminance data is generated. In this setting example, since theweighting factor in the intermediate transient region is rectilinearlychanged, operation processing is simple in generating the weightingfactor and luminance data in the transient region.

Another example of setting of weighting factor based on edge informationwill now be described by way of FIG. 16. The setting of weighting factora in this setting example is identical to the foregoing setting examplein that: when the detected spatial frequency f is a low frequency lowerthan s, the weighting factor a is set to 0.5 and luminance data based onY=(R+2G+B)/2 is thereby generated at the mixed luminance data generatingsection 21; and, when the detected spatial frequency f is a highfrequency higher than t, the weighting factor a is set to 1 andluminance data based on Y=2G is thereby generated at the mixed luminancedata generating section 21. When detected spatial frequency is s<f<t inthis setting example, i.e., if the detected spatial frequency is of amedium level, the weighting factor a is to be set as having a functionalrelationship {a=F(f)} so that it is changed smoothly in a curve from 0.5to 1.

In this case, luminance data based on Y=2G×F(f)+(R+B){1−F(f)} isgenerated from the mixed luminance data generating section 21.Accordingly, since weighting factor a is smoothly changed in theintermediate frequency region between the low-frequency region and thehigh-frequency region, a smooth change is possible of the luminance dataat the boundary of each region and of edge signals based on the same foruse in enhancement processing.

Yet another example of setting of weighting factor based on detectedspatial frequency will now be described by way of FIG. 17. In thissetting example, weighting factor a for the lowest frequency portion ofthe spatial frequencies detected at the edge detection means is set to0.5 and weighting factor a for the highest frequency portion is setto 1. Weighting factor a between these is set as having a functionalrelationship {a=F(f)} indicating a curve smoothly connecting thelow-frequency region, medium frequency region and high-frequency regionbetween these irrespective of the threshold values s, t.

In this case, luminance data is generated on the basis ofY=2G×F(f)+(R+B) {1−F(f)} from the mixed luminance data generatingsection 21. Accordingly, it is possible to change weighting factor asmoothly in the manner of a curve over the regions of detected spatialfrequency and the luminance data based on the same and edge signals foruse in enhancement processing can be outputted as even more smoothlychanged.

A fifth embodiment of the invention will now be described. FIG. 18 is ablock diagram showing the fifth embodiment wherein the like componentsas in the first to fourth embodiments are denoted by like referencenumerals and description thereof will be omitted. This embodiment isachieved as a combination of the first embodiment shown in FIG. 3 andthe third embodiment shown in FIG. 13. In particular, switching is madecorresponding to the manner of image furthermore between the switchingof luminance data generation technique based on color information andthe switching of luminance data generation technique based on edgeinformation. In other words, when the switching of luminance datageneration technique based on detection of color information and theswitching of luminance data generation technique based on detection ofedge information are used in combination, switching must be made betweenthese two detection results. In this embodiment, regions in an image areseparated for example into those regions with frequent edges and otherregions. The switching of luminance data generation technique based ondetection of edge information is used for the regions with frequentedges. The switching of luminance data generation technique based oncolor information is used for the other regions. It is thereby possibleto generate more suitable luminance data as well as edge signals for usein enhancement processing in a manner corresponding to the object.

Concrete construction of this embodiment will now be described.Referring to FIG. 18, denoted by numeral 41 is an image regiondetermination means for making a coarse determination as to whetherthere are many edge portions or not within an image (the state of beingfrequent/infrequent of edge portions) for example for each ofpredetermined divided regions of Bayer RGB array image which has beensubjected to white balancing. A second selector 42 provides an output inaccordance with a selection signal based on the result of determinationat the image region determination means 41 by selecting from theselection signal based on edge information detected at the edgedetection means 31 and the selection signal based on color informationdetected at the color information detection means 6.

In this embodiment thus having the image region determination means 41and selector 42, if for example it is determined as that a large numberof edges exist in a certain region of the image and that edgeinformation is predominant concerning the selection of luminance datageneration technique, a selection signal based on edge informationdetected by the edge detection means 31 is used as the selection signalof selector 10 for selecting from the outputs of the first and secondluminance data generating sections 8, 9. On the other hand, if it isdetermined as that the number of edges is small and color information ispredominant in the image region, a selection signal based on colorinformation detected by the color information detection means 6 is usedas the selection signal of selector 10 for selecting from the outputs ofthe first and second luminance data generating sections 8, 9. It isthereby possible to generate more suitably and efficiently luminancedata and edge signals for use in enhancement processing corresponding tothe manner of each region in the image.

While the above fifth embodiment is a combination of the firstembodiment and third embodiment, a combination is also possible of thesecond embodiment and fourth embodiment which is shown in FIG. 19 as asixth embodiment. In particular, the sixth embodiment is achieved byadding an image region determination means 41 and a second selector 42in a similar manner as in the above fifth embodiment to a combination ofone having a single mixed luminance data generating section 21 and aweighting factor generating section 22 for generating weighting factorat the mixed luminance data generating section 21 based on colorinformation and one having a single mixed luminance data generatingsection 21 and a weighting factor generating section 33 for generatingweighting factor at the mixed luminance data generating section 21 basedon edge information so as to selectively use the weighting factor basedon color information and that based on edge information. It is therebypossible to generate luminance data and edge signals for use inenhancement processing corresponding to the manner of each region in theimage more suitably and efficiently and without unnaturalness at theboundaries thereof.

A seventh embodiment of the invention will now be described. In general,methods for forming a large one piece of image by joining a plurality ofimages are used for example in making a panoramic picture. If differentedge (contour) enhancement processing techniques are used at the jointboundary portions when making a panoramic picture by means of suchjoining of a plurality of images, unnaturalness due to the difference inprocessing remains to occur at such boundary portions.

The seventh embodiment is constructed so that, when the presentinvention is applied to image processing apparatus for making a largeone frame of image such as the above panoramic picture by joining aplurality of images, the same luminance data generating technique isused at the boundary of joining of images adjoining each other so as notto leave unnaturalness in edge enhancement processing at the jointboundary portions as described above.

FIG. 20 is a block diagram showing a seventh embodiment wherein the likecomponents as in the first embodiment shown in FIG. 3 are denoted bylike reference numerals and description thereof will be omitted.Additionally provided components in this embodiment are a jointdetermining section 51 and memory 52. The joint determining section 51is for detecting a joint portion of two pieces of images to be joinedadjoining each other. The joint portion is determined by using atechnique such as one disclosed in Japanese patent application laid openHei-7-203278, i.e., the technique in which contrast information of imageis used to detect which portions of the images correspond to each other.Memory 52 is designed to store by each pixel as to which one of theluminance data generation techniques of the first and second luminancedata generating sections is selected in a first piece of image to bejoined.

Operation of the seventh embodiment thus constructed will now bedescribed. First, in processing of the first piece of image, nooperation is performed at the joint determining section 51; on the otherhand, data is stored to memory 52 by each pixel as to which one of theluminance data of the first and second luminance data generatingsections 8, 9 is selected by the selector 10. Next, in processing of asecond piece of image adjoining the first piece, the joint determiningsection 51 detects which portions in the first and second pieces ofimage correspond to each other so as to determine a joint boundaryportion of the second piece of image. The luminance data generationtechnique selected in generation processing of luminance data at thejoint boundary portion of the first piece of image corresponding to thedetected joint boundary portion is then read out from memory 52 and theluminance data of the joint boundary portion of the second piece ofimage is generated by using in a forced manner the same luminance datageneration technique. Further, the luminance data other than those inthe joint boundary portion of the second piece of image are generated bya luminance data generation technique based on color information. Itshould be noted that the switching of luminance data generationtechnique at the joint boundary portion and at those other than theboundary portion are performed for every pixel.

Then, at the same time of performing generation processing of luminancedata of the whole area including the joint boundary portion of thesecond piece of image, data is stored to memory 52 as to which one ofthe luminance data generation techniques is selected in the luminancedata generation processing of the second piece of image. Processing of athird piece and thereafter adjoining the second piece is then performedin a similar manner so as to generate a plurality of images which areenhanced of edges. The joining processing of each image is performed ina joining processing section (not shown) at a subsequent stage. It isthereby possible to obtain a joined image such as a panoramic pictureenhanced of edges without unnaturalness at joint boundary portions.

It should be noted that, in the above embodiment, selector informationcorresponding to one piece of image must be stored to memory 52 in orderto perform real-time processing of image outputted from the image pickupmeans. If image data is previously stored to a memory or the like,however, it suffices to store to the memory only the selectorinformation corresponding to joint portions, since it is possible topreviously determine the joint portions. Further, in this embodiment,information of saturation, hue or “saturation+hue” can be used as thecolor information to be detected by the color information detectionmeans in a similar manner as in the first embodiment. Furthermore, thetechnique for detecting color information by each pixel signal of imagesignals, the technique for detecting an average color information of awhole image, the technique for detecting an average color information ofone whole frame from specific sampling data of image signals, etc., canbe used as the detection technique of color information at the colorinformation detection means.

While the above seventh embodiment has been shown as the embodiment ofthe case of applying the first embodiment to an image processingapparatus having a processing section for joining a plurality of images,it is also possible to apply the above second to sixth embodiments tothe image processing apparatus having the joining processing section.Such application of the second embodiment is shown as an eighthembodiment in FIG. 21. When a single mixed luminance data generatingsection 21 and a weighting factor generating section 22 are provided asin the eighth embodiment, stored to memory 52 are weighting factorswhich have been set in the luminance signal generation processing ofjoining images. In this embodiment, the luminance data generated from Gsignals and the luminance signal generated from all color signals aremixed with continuously changing the mixing ratio on the basis of colorinformation and joint information so as to generate mixed luminancedata. A weighting factor is then set by each pixel based on the jointinformation for the joint boundary portions of image and a weightingfactor is set on the basis of color information for those other than thejoint boundary portions. Hence edge enhancement processing can beperformed smoothly and without unnaturalness at the boundary portions inperforming joining processing of a plurality of images.

An application of the third embodiment to an image processing apparatushaving a joining processing section is shown as a ninth embodiment inFIG. 22. In this embodiment, output is switched based on edgeinformation and joint information between the luminance data from thefirst luminance data generating section 8 for finding luminance datafrom G signals and the luminance data from the second luminance datagenerating section 9 for finding luminance data from all color signals.Hence edge enhancement processing can be performed without unnaturalnessat the boundary portions in performing joining processing of a pluralityof images even for images having frequent edges.

It should be noted that, also in this embodiment, 2G or (R+2G+B)/2 canbe used as the luminance signal in finding edges from an image at theedge detection means 31 in a similar manner as in the third embodiment.Further, in switching the luminance data generation technique based onedge information and joint information, the switching is performed forevery pixel based on joint information for the joint boundary portionsof image and the switching is performed based on edge information forthose other than the joint boundary portions of image.

An application of the fourth embodiment to an image processing apparatushaving a joining processing section is shown as a tenth embodiment inFIG. 23. In this embodiment, mixed luminance data is generated by mixingthe luminance data generated from G signals and the luminance datagenerated from all color signals with continuously changing the mixingratio based on edge information and joint information. It is therebypossible in performing joining processing of a plurality of images toperform edge enhancement processing smoothly and without unnaturalnessat the boundary portions thereof even for images having frequent edgeportions. Further, weighting factor a at the weighting factor generatingsection for setting the mixing ratio is generated for every pixel on thebasis of joint information of image for the joint boundary portions ofimage and on the basis of edge information of image for those other thanthe joint boundary portions of image.

An application of the fifth embodiment to an image processing apparatushaving a joining processing section is shown as an eleventh embodimentin FIG. 24. In this embodiment, output is provided as switched by thesecond selector (selector of selection signals) 42 between the selectionsignal for controlling the switching of selector 10 for switchingluminance data based on color information and the selection signal forcontrolling the switching of selector 10 for switching luminance databased on edge information on the basis of joint information of imagefrom the joint determining section 51 for the joint boundary portions ofimage and on the basis of determination signals of the image regiondetermining section 41 for those other than the joint boundary portionsof image. It is thereby possible in performing joining processing toperform edge enhancement processing corresponding to the characteristicof an object at favorable S/N and without unnaturalness at the jointportions.

An application of the sixth embodiment to an image processing apparatushaving a joining processing section is shown as a twelfth embodiment inFIG. 25. In this embodiment, output is provided as switched by thesecond selector 42 between the weighting factor a from the weightingfactor generating section 22 for setting the mixing ratio at the mixedluminance data generating section 21 based on color information and theweighting factor a from the weighting factor generating section 33 forsetting the mixing ratio at the mixed luminance data generating section21 based on edge information on the basis of joint information of imagefrom the joint determining section 51 for the joint boundary portions ofimage and on the basis of determination signals from the image regiondetermining section 41 for those other than the joint boundary portionsof image. It is thereby possible in performing joining processing of aplurality of images to perform edge enhancement corresponding to thecharacteristic of an object smoothly at favorable S/N and withoutunnaturalness at the joint portions.

As has been described by way of the above embodiments, it becomespossible in accordance with the first aspect of the invention to extractedge enhancing components on the basis of an optimal luminance datacorresponding to color information so that an image processing apparatuscan be achieved as capable of performing edge enhancement processing atfavorable S/N and with less occurrence of edge noise in high-saturationregions and/or low-saturation regions. According to the second aspect ofthe invention, an optimal luminance data corresponding to colorinformation can be smoothly changed so that edge enhancement processingwithout unnaturalness can be performed. According to the third aspect ofthe invention, it becomes possible to perform edge enhancementprocessing on the basis of an optimal luminance data corresponding toedge information even for an image having frequent edge portions.According to the fourth aspect of the invention, an optimal luminancedata corresponding to edge information can be smoothly changed so thatedge enhancement processing without unnaturalness can be performed evenfor an image having frequent edge portions. According to the fifthaspect of the invention, edge enhancement processing at favorable S/Ncan be performed corresponding to the characteristic of an object.According to the sixth aspect of the invention, edge enhancementprocessing can be performed corresponding to the characteristic of anobject smoothly at favorable S/N and without unnaturalness.

According to the seventh aspect of the invention, when joining aplurality of images, edge enhancement processing can be performedwithout unnaturalness at the joint portions. According to the eighthaspect of the invention, when joining a plurality of images, edgeenhancement processing can be performed smoothly and withoutunnaturalness at the joint portions. According to the ninth aspect ofthe invention, when joining a plurality of images, edge enhancementprocessing without unnaturalness at the joint portions can be performedeven for an image having frequent edge portions. According to the tenthaspect of the invention, when joining a plurality of images, edgeenhancement processing can be performed smoothly and withoutunnaturalness at the joint portions even for an image having frequentedge portions. According to the eleventh aspect of the invention, whenjoining a plurality of images, edge enhancement processing can beperformed corresponding to the characteristic of an image at favorableS/N and without unnaturalness at the joint portions. According to thetwelfth aspect of the invention, when joining a plurality of images,edge enhancement processing can be performed corresponding to thecharacteristic of an object smoothly at favorable S/N and withoutunnaturalness at the joint portions.

1. An image processing apparatus having a processing section forenhancing edges in an image, said image processing apparatus comprising:image pickup means for converting an object light into image signals ofBayer RGB array; color information detection means for detecting colorinformation of an object from the image signals obtained by the imagepickup means; a mixed luminance data generation means for generatingmixed luminance data by mixing luminance data for use in edgeenhancement processing generated from G signals out of the image signalsobtained by said image pickup means and luminance data for use in edgeenhancement processing generated from all color signals of the imagesignals with continuously changing a mixing ratio; and means for settingthe mixing ratio at said mixed luminance data generation means based onthe color information obtained at said color information detectionmeans.
 2. The image processing apparatus according to claim 1, whereinthe color information detected by said color information detection meansis saturation information of said image.
 3. The image processingapparatus according to claim 1, wherein the color information detectedby said color information detection means is hue information of saidimage.
 4. The image processing apparatus according to claim 1, whereinthe color information detected by said color information detection meansis saturation information and hue information of said image.
 5. Theimage processing apparatus according to any one of claims 1 to 4,wherein said color information detection means detects color informationfor every pixel signal of said image signals.